Conventional mass storage devices include a spindle motor of the mass storage device that applies mechanical energy to rotate the recording medium. Conventional approaches to reducing wear on various parts of the mass storage device during spin-up and spin-down focus on reducing the time to complete spin-up or spin-down. The approaches to reducing the time includes optimization of the application of current to the spindle motor of the mass storage device to uniformly decrease current input throughout the entire spin-up process, and improving the mechanics of the spindle motor of the mass storage device to improve use of available current. Reducing wear by reducing the time to complete spin-up or spin-down incorrectly assumes that wear of the interface is reduced by reducing the linear sliding contact distance of a head and a rotating disc. This assumption is incorrect because impacts from the dynamic response of the head as the head slides across the rotating disc contribute a considerable extent of damage to the head and the disc. The wear is accentuated for a disc having laser textured bumps in a landing zone.
During the initialization, temporary anomalies in the rotation typically occur that increases the wear on various parts of the mass storage device, including a read/write head. The anomalies include the cessation of the air bearing of the read/write head, either during an intermittent bounce off of the disc, or a longer term sliding of the head on the rotating disc.
FIG. 1 is a chart 100 of a relationship between input current and time in a conventional mass storage device during initialization. During initialization, also known as spin-up, of the mass storage device, the spindle motor of the mass storage device receives a substantially linear monotonically decreasing quantity of current 110. The current 110 is linearly decreased from the beginning time of the initialization t0 120, through various other times, such as t1 130, t2 140, and t3 150, until a target rotation speed is achieved at time t4 160, after which, a decreased and constant quantity of current 110 is applied to the motor to maintain the target rotation speed.
FIG. 2 is a chart 200 of a relationship between available torque and time in a conventional mass storage device during initialization. In general, the quantity of available torque 210 decreases during spin-up of the disc. The quantity of available torque 210 decreases from the beginning time of the initialization t0 220, through various other times, such as t1 230, t2 240, and t3 250, until a target rotation speed is achieved at time t4 260, after which, no torque is available when the quantity of current input to the motor is held constant, as shown in FIG. 1, to maintain the target rotation speed.
In FIG. 2, the available torque 210 is less than maximum between times t0 220 and t1 230, while the head is sliding on the rotating disc. When the head flies over the rotating disc on an air bearing, between times t1 230 and t2 240, the available torque 210 increases. However, when an anomaly occurs, such as the cessation of the head flying on an air bearing, either during an intermittent bounce off of the disc, or a longer term sliding of the head on the rotating disc, the available torque 210 decreases during that time. For example a decrease in available torque 210 occurs between times t2 240 and t3 250 during a cessation of the head flying on an air bearing while the head slides on the rotating disc. Thereafter, when the head resumes flying over the rotating disc on an air bearing, between times t3 250 and t4 260, the available torque 210 gradually decreases as the rotation speed increases, as shown in FIG. 3.
FIG. 3 is a chart 300 of a relationship between rotation speed of the disc and time in a conventional mass storage device during initialization. In general, the rotation speed (RPM) 310 rises during spin-up of the disc. The rotation speed 310 increases from the beginning time of the initialization t0 320, through various other times, such as t1 330, t2 340, and t3 350, until a target rotation speed is achieved at time t4 360. After the target rotation speed is achieved, the rotation speed 310 is held substantially constant through a constant input of current, as shown in FIG. 1.
In FIG. 3, the rotation speed 310 is less than maximum between times t0 320 and t1 330, while the head is sliding on the rotating disc. When the head flies over the rotating disc on an air bearing, between times t1 330 and t2 340, the rotation speed 310 increases.
However, when an anomaly occurs, such as the cessation of the head flying on an air bearing, either during an intermittent bounce off of the disc, or a longer term sliding of the head on the rotating disc, the rate of acceleration in the rotation speed 310 slows. The rate of acceleration in the rotation speed 310 slows to no lower than zero, in which the rotation speed 310 holds steady. For example, a decrease in acceleration of rotation speed 310 occurs between times t2 340 and t3 350 during a cessation of the head flying on an air bearing while the head slides on the rotating disc.
After time t3 350, the head resumes flying over the rotating disc on an air bearing. Between times t3 350 and t4 360, the rotation speed 410 gradually rises until the target rotation speed is achieved.
FIG. 4 is a chart 400 of a relationship between drag and time in a conventional mass storage device during initialization. In general, drag 410, decreases during spin-up of the disc. The drag 410 generally decreases from the beginning time of the initialization t0 420, through various other times, such as t1 430, t2 440, and t3 450, until a rotation speed is achieved at time t4 460. After the target rotation speed is achieved, the drag 410 remains substantially constant through a constant input of current, as shown in FIG. 1.
In FIG. 4, the drag 410 is substantially at maximum between times t0 420 and t1 430, while the head is sliding on the rotating disc. When the head flies over the rotating disc on an air bearing, between times t1 430 and t2 440, the drag 410 decreases. However, when an anomaly occurs, such as the cessation of the head flying on an air bearing, either during an intermittent bounce off of the disc, or a longer term sliding of the head on the rotating disc, the drag 410 increases during that time. For example an increase in drag 410 occurs between times t2 440 and t3 450 during a cessation of the head flying on an air bearing while the head slides on the rotating disc. Thereafter, when the head resumes flying over the rotating disc on an air bearing, between times t3 450 and t4 460, the drag 410 gradually decreases until the target rotation speed is achieved. Thereafter, drag 410 remains at a relatively low and substantially constant level.
One conventional solution is to apply maximum current to the spindle motor of the mass storage device from the beginning of initialization, until the target rotation speed is achieved. However, this solution requires the implementation of a full power generation power supply in the mass storage device, which not only is relatively expensive apparatus, but also requires an external power supply because batteries can not supply sufficient power. As a result, applying full current throughout the entire spin-up process is not feasible. Furthermore, a mass storage device has limited quantities of power available. In addition, the use of maximum current through the entire spin-up process generates relatively large quantities of heat, which requires relatively more heat-resistant material in the mass storage device, which increases the weight and expense of the mass storage device.
Furthermore, during initialization, there are time periods when applying full maximum current to the spindle motor is not required in order to avoid anomalies. For example, in FIG. 1, between time t3 150 and time t4 160, the current 110 is less than the maximum current, yet, as shown in FIG. 4, between time t3 450 and time t4 460, the drag 410 is substantially less than maximum, and the drag 410 decreases over time. In this example, increasing the current 110 yields diminishing reductions a head/disc wear. Therefore, there are time periods in the initialization of the mass storage device where applying maximum current is a poor use of the limited quantities of power.
What is needed is a system, method and/or apparatus that manages or controls the input current to the spindle motor of the mass storage device in a manner that reduces the wear on the head and recording medium, yet provides efficient use of the limited power available to the mass storage device. More specifically, what is needed is a system, method and/or apparatus that manages or controls the input current to the spindle motor of the mass storage device that reduces the impact of drag, and increases the rotation speed and available torque during cessation of the head flying on an air bearing.